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VOL. 62, NO. 1 (MARCH 2009) P. 96–101 Status of High Arctic Black-Legged (Rissa tridactyla) Colonies in Barrow Strait, Nunavut, Canada MARK L. MALLORY,1,2 JASON A. AKEAROK1 and ANTHONY J. GASTON3

(Received 18 January 2008; accepted in revised form 7 April 2008)

ABSTRACT. We used aerial survey estimates, photographic censuses, and plot counts to examine trends in the size of five black- legged kittiwake (Rissa tridactyla) colonies around Barrow Strait, eastern Nunavut, Canada, between 1972 and 2007. During these three decades, one small colony disappeared, two medium-sized colonies showed no overall trend, and one moderate and one large colony appeared to increase in size. Collectively, the number of breeding in this region may have increased by over 40%. Counts of kittiwakes at some colonies were markedly low in 2003, following two consecutive years of late, extensive sea ice, although overall there was no significant relationship between numbers of kittiwakes attending colonies and sea-ice extent in Barrow Strait and Lancaster Sound. It is not known why kittiwake colonies in High Arctic Canada have apparently increased while those in West and elsewhere have declined, or what factors influenced these changes. Key words: black-legged kittiwake, Rissa tridactyla, Arctic, population trend

RÉSUMÉ. Entre 1972 et 2007, à l’aide d’estimations effectuées à partir de levés aériens, de recensements photographiques et de dénombrements, nous avons examiné les tendances caractérisant la taille de cinq colonies de mouettes tridactyles (Rissa tridactyla) dans les environs du détroit de Barrow, dans l’est du Nunavut, au Canada. Pendant ces trois décennies, une petite colonie a disparu, deux colonies de taille moyenne n’ont affiché aucune tendance générale, tandis que la taille d’une colonie de taille modérée ainsi que celle d’une colonie de grande taille ont semblé augmenter. Collectivement, le nombre de mouettes tridactyles se reproduisant dans cette région pourrait s’être accru de plus de 40 pour cent. En 2003, le nombre de mouettes tridactyles de certaines colonies était nettement bas, ce qui suivait deux années consécutives de glace de mer tardive et étendue bien que dans l’ensemble, il n’existait pas de relation importante entre le nombre de mouettes tridactyles faisant partie des colonies et l’étendue de la glace de mer dans le détroit de Barrow et le bras de mer de Lancaster. On ne sait pas pourquoi les colonies de mouettes tridactyles de l’Extrême-Arctique sembleraient avoir pris de l’ampleur, tandis que les colonies de l’ouest du Groenland et d’ailleurs se sont amincies. De plus, on ne connaît pas les facteurs qui ont influencé ces changements. Mots clés : mouette tridactyle, Rissa tridactyla, Arctique, tendance caractérisant la population

Traduit pour la revue Arctic par Nicole Giguère.

INTRODUCTION that includes colonies situated in the eastern Canadian Arc- tic (Brown et al., 1975). Recently concerns have been raised are a ubiquitous feature of the Canadian Arctic over declining numbers of kittiwakes at colonies around the marine environment, with millions of migrating to North , from the (Frederik- this region to breed and feed during the brief Arctic sum- sen et al., 2004) west to Greenland (Nyeland, 2004). Popu- mer (Brown et al., 1975; Mallory and Fontaine, 2004). As lation reductions have been attributed principally to changes seabirds are strong indicators of the health of the marine in marine food supplies linked to climate change and effects ecosystem (Cairns, 1987; Montevecchi, 1993), long-term of commercial fisheries. monitoring of populations provides an index of Although the kittiwake has been studied elsewhere in its overall changes in the marine food web (e.g., Frederiksen breeding range (Baird, 1994), little research has been con- et al., 2004). Indeed, seabird monitoring in Arctic Canada ducted on the in Arctic Canada, despite the fact that has detected progressive shifts in the relative abundance of the region supports an estimated 95 000 breeding pairs, or small forage fish in response to changing climate, as well as 48% of the Canadian breeding population (Mallory and the effects of late, extensive sea ice on marine productivity Fontaine, 2004). Studies have been limited to regional sur- (Gaston and Hipfner, 1998; Gaston et al., 2003, 2005a). veys in the 1970s (e.g., Brown et al., 1975), contaminant The black-legged kittiwake (Rissa tridactyla) is a small monitoring (Braune, 2007), a single-season study in the marine with a circumpolar distribution (Baird, 1994) Low Arctic (Gaston, 1988), and a multi-year assessment of

1 Environment Canada, Canadian Wildlife Service, Box 1714, Iqaluit, Nunavut X0A 0H0, Canada 2 Corresponding author: [email protected] 3 Environment Canada, National Wildlife Research Centre, Raven Road, Carleton University, Ottawa, Ontario K1A 0H3, Canada © The Arctic Institute of North America HIGH ARCTIC KITTIWAKE COLONIES • 97 breeding biology at one site in Lancaster Sound (Gaston et al., 2005b). However, recently we had the opportunity to census kittiwake colonies around Barrow Strait in the Cana- dian High Arctic archipelago (Fig. 1), as part of regional surveys for ivory (Pagophila eburnea; Robertson et al., 2007). In this paper, we report on the population status of four colonies, as well as the trends in population size at one major colony inferred from three decades of intermittent plot monitoring. We also assess the suggestion by Alliston et al. (1976) that interannual variation in sea-ice distribution in this region leads to interannual variation in colony attend- ance, and specifically that fewer kittiwakes attend their colonies during breeding seasons when sea ice around the colony breaks up later, or is abnormally extensive.

METHODS FIG. 1. Locations of black-legged kittiwake colonies around Barrow Strait in Our work focused on the five kittiwake colonies found the eastern Canadian Arctic. around Barrow Strait in eastern Nunavut, Canada (Fig. 1), and specifically on Browne Island, Baillie-Hamilton Island, we aggregated counts from more plots representing fewer Separation Point (Cornwallis Island), Batty Bay (Somerset years. Island), and Prince Leopold Island. Aerial surveys of these We measured the distance from each colony to open colonies were conducted in July–August 1972 and 1973, water (or < 50% ice cover) during the third week of June and June–August 1974 and 1975 (Nettleship, 1974; Brown each year, using archived sea ice distribution maps avail- et al., 1975; Alliston et al., 1976). These surveys generally able at the Environment Canada – Canadian Ice Serv- consisted of a single flight from fixed-wing aircraft, during ice Archive (http://ice-glaces.ec.gc.ca/App/WsvPageDsp. which colony size was estimated. We used the published, cfm?ID=11872&Lang=eng). For Prince Leopold Island, estimated colony size from those surveys as our initial base- following Gaston et al. (2005b), we scored the distance as line (Table 1). For more recent censuses of the first four “0” if the floe edge was at the colony, positive values if the sites, we traveled to the colony by Bell 206L helicopter in floe edge was east of the colony (i.e., if sea ice was more the first week of July 2003–07. We hovered ~500 m from extensive in Lancaster Sound), and negative values if the the colony (Batty Bay, Baillie-Hamilton, Separation Point), floe edge was west of the colony (i.e., if sea ice was less or landed and walked along the front of the colony (Browne extensive in Lancaster Sound). Island), and then used a Canon® EOS 20D digital camera Trends in colony size were assessed for Prince Leopold with a Canon EF 100–400 mm zoom lens (image stabilizer, Island by conducting a linear regression of log10 transformed 1:4.5–5.6) to produce a series of high-resolution, 8 mega- plot counts against year. The only other colony with suffi- pixel photographs that encompassed each colony. These cient data for a temporal comparison was Browne Island, digital photographs were downloaded to computers and where we compared counts from the 1970s to the 2000s assembled in Microsoft® Powerpoint to produce an image using a t-test. To assess whether colonies had fewer kitti- of the entire colony at each site. Kittiwakes were counted wakes in attendance during years when sea ice was more from these images, with one exception. On Browne Island extensive, we created standardized values (Z scores) within in 2003, two people counted all kittiwakes from the beach each colony for annual kittiwake census or plot counts, as 100–200 m in front of the colony, using 10 × 42 binoculars well as a standardized distance to open water (ice edge), or a 60× spotting scope. thereby scaling all colonies to the same relative size and At Prince Leopold Island, long-term monitoring plots ice-edge distance. We then pooled data across colonies and were established on kittiwake breeding areas in the 1970s regressed standardized annual colony size on standardized (G, M, Qupper, Qlower, Qnorth, S, T; Nettleship, 1977; distance to the ice edge. Gaston et al., 2005b), and kittiwakes on these plots were counted daily whenever research teams were on the island between 1975 and 2008. Because of inclement weather RESULTS (notably fog), not all plots could be counted each day, and in some years certain plots were under-represented. We used Browne Island the annual mean count of birds prsent daily between 15 July and 15 August for plots G and M, because this figure This colony is situated on east-facing, 100 m high sedi- maximized the number of years for which there were data mentary cliffs, and the site has been censused eight times (n = 9), but we note that the patterns were consistent when since 1972. Estimated colony size has ranged from 1000 98 • M.L. MALLORY et al.

TABLE 1. Black-legged kittiwake colonies in the Canadian High Arctic that have recently been reassessed, showing locations and census estimates made since 1972. All counts from 2003 to 2007 are new data from this study.

Location Colony Census Name Latitude (˚N) Longitude (˚W) Year Size Reference

Washington Point, Baillie-Hamilton Island 75.77 94.28 1972 1000 Nettleship, 1974 1973 6000 Brown et al., 1975 2003 3464 2006 5488 2007 6273 Separation Point, Cornwallis Island 75.12 93.48 1972 250 Nettleship, 1974 2005 0 2006 0 Browne Island 74.82 96.36 1972 2000 Brown et al., 1975 1974 4000 Alliston et al., 1976 1975 1000 Alliston et al., 1976 2003 1692 2004 3430 2005 3221 2006 3941 2007 3689 Batty Bay, Somerset Island 73.22 91.42 1974 700 Alliston et al., 1976 1975 4000 Alliston et al., 1976 2007 10 007 individuals (1975) to 4000 individuals (1974), with a max- 2.5 times the colony size estimated in 1975, and 14 times the imum, photo-based count of 3941 individuals in 2006 700 individuals present in 1974, suggesting an increase in (Table 1). The mean estimated colony size in the 1970s the size of the colony. (2333 ± 883 SE, n = 3) did not differ from counts of kitti- Using maximum estimates from 1973–75 for Browne wakes at the colony since 2003 (3195 ± 395, n = 5; Welch’s t2 Island, Baillie-Hamilton Island, and Batty Bay, these sites = 0.9, p = 0.46), and annual census estimates have exhibited supported approximately 14 000 kittiwakes. However, in high variability (coefficient of variation [SD/mean] 40%). early July 2007, we counted 19 969 kittiwakes at these col- onies, an apparent increase of 43%, due principally to the Washington Point, Baillie-Hamilton Island much higher numbers of birds found at Batty Bay in 2007.

The colony at Washington Point, situated on sheer, Prince Leopold Island southeast-facing, 200 m high cliffs, has been censused five times since 1972. Colony size has ranged from 1000 (1972) This large kittiwake colony (~ 29 000 pairs; Nettleship, to 6273 (2007) kittiwakes. Like Browne Island, this site 1980) is situated principally on the east side of the island, showed no obvious temporal trend in numbers of kittiwakes on sheer, 330 m cliffs, among nesting thick-billed murres (Table 1), and annual counts have also been highly variable ( lomvia) and northern fulmars (Fulmarus glacialis). (CV 50%). Although no complete colony census has been made since the initial census in 1973, kittiwakes attending breeding Separation Point, Cornwallis Island plots have been counted in 10 years since 1975. The mean number of kittiwakes counted on the study plots from 20 This colony supported 250 kittiwakes in 1972 (Table 1; July to 6 August was 409 ± 21 SE birds in five years between Brown et al., 1975). However, surveys in early July 2005 and 1975 and 1988, but 611 ± 74 SE birds for five years between 2006 found no kittiwakes at the site, and although lichens 2001 and 2008 (Fig. 2), an apparent increase of 49%. This (Xanthoria, formerly Caloplaca) were found on the cliffs increasing trend in plot counts was statistically significant 2 and two pairs of glaucous gulls ( hyperboreus) were (r = 0.60, F1,8 = 12.1, p < 0.005), described by the following present, there was no evidence (old nests or faecal remains) relationship: to indicate recent use by kittiwakes. This colony appears to have been abandoned. log10(Plot Count) = 0.0090*(Year) – 15.278

Batty Bay, Somerset Island Sea Ice Distribution and Colony Size

This spectacular colony is situated on east-facing, sheer, In the third week of June each year, kittiwakes had to 330 m high cliffs, and many of the kittiwake nests are travel as much as 200 km to reach areas with less than 50% located behind a waterfall. The colony has been counted ice cover (except for small leads that were not marked on only three times since 1974, with a maximum count of maps; Fig. 3a). For the three smaller colonies, fewer kitti- 10 007 kittiwakes in 2007 (Table 1). However, this count is wakes were counted in years with more extensive sea ice, HIGH ARCTIC KITTIWAKE COLONIES • 99 but only at Baillie-Hamilton Island was this correlation sig- nificant r( s5 = - 0.97, p = 0.02). Because there was a signif- icant increase in kittiwakes at Prince Leopold Island over the 30-year period (above), we separated annual counts into pre-2000 and post-2000 categories. We calculated the dif- ference between annual mean plot counts in each period and the overall average for that period to create a residual plot count for each year. Using these residuals, numbers of kit- tiwakes were not significantly correlated with distance to the ice edge at Prince Leopold Island (Fig. 3b; rs9 = - 0.05, p = 0.9). Pooling standardized colony or residual plot count and distance to ice edge values for all colonies, we found a general pattern of fewer kittiwakes at colonies in years with more extensive ice, but this relationship was not signifi- cant (r25 = - 0.27, p = 0.19). Despite this, we noted that since 2001, the lowest counts of kittiwakes at Browne Island, Bail- lie-Hamilton Island, and Prince Leopold Island all occurred in 2003 (Table 1), following two consecutive years of late, extensive sea ice and consequent poor reproduction in Lan- caster Sound (Gaston et al., 2005b).

FIG. 2. Trends in black-legged kittiwake numbers from an index of plot counts DISCUSSION (1976 = 100) at the Prince Leopold Island colony.

Our evidence suggests that there are perhaps 78 000 recent years, although large-format photographs were taken black-legged kittiwakes breeding around Barrow Strait, of some sites. In many cases, original estimates of colony Nunavut (41% of the estimated Canadian Arctic kittiwake sizes for kittiwakes and fulmars (Fulmarus glacialis) were population; Mallory and Fontaine, 2004), which represents too high, and in subsequent years counts were reduced as an increase from estimates in the 1970s. This contrasts other survey techniques were applied (e.g., Brown et al., somewhat to the pattern found in nearby Greenland, where 1975; Gaston et al., 2006) or original estimates were reas- kittiwake numbers declined in the 20th century (Nyeland, sessed from photograph counts (Nettleship, 1980). Thus, the 2004). However, as in Greenland, there was considerable 14 000 kittiwakes at the three smaller colonies in the 1970s variability in annual and long-term colony size. may have been an overestimate. Second, some local Inuit Annual variation in the size and occupancy of kittiwake hunters at Pond Inlet have reported that breeding kittiwakes colonies has been observed previously for colonies in Brit- have apparently increased at the Cape Graham Moore col- ain (Coulson, 1983) and eastern Canada (Chapdelaine and ony at the eastern entrance to Lancaster Sound, noting that Brousseau, 1989). Some black-legged kittiwakes will emi- more kittiwakes now nest there in places formerly occupied grate from one breeding colony to another in response to by murres (J. Akearok, unpubl. data). Such an observation poor feeding or breeding conditions (Danchin et al., 1998; would be consistent with an overall increase in kittiwake Suryan and Irons, 2001). However, these studies examined numbers in this region. movements among numerous colonies of kittiwakes situated While numbers may have increased at some colonies, we within ~100 km of each other, and in locations without sea did note the loss of one small colony at Separation Point. ice. In our study, there were only five colonies in the region, Colony dynamics of kittiwakes vary with colony size and most were at least 100 km from each other. More- (Danchin et al., 1998; Suryan and Irons, 2001), and Chap- over, in the Arctic, it seems likely that the constraints of a delaine and Brousseau (1989) found that moderate-sized short period of available food and extensive sea ice would colonies grew in the Gulf of St. Lawrence, Canada, while strongly favour birds that had experience with feeding con- small colonies remained stable. We do not know why the ditions near their colony, so we anticipate selection against Separation Point colony disappeared, or for how long it may intercolony movements. have existed. In a similar pattern, many small colonies of Whether or not some of the variation in colony size was ivory gulls have also disappeared in the Canadian High due to emigration, the overall increase of more than 40% at Arctic in recent years, while one large one persists (Robert- the smaller colonies, as well as on the study plots at Prince son et al., 2007). Leopold Island (PLI), suggests a real increase in the number We failed to find a significant relationship between the of kittiwakes breeding around Barrow Strait. Two other distance to open water during late June (around the time lines of evidence support this conclusion. First, estimates that birds would be initiating nesting) and numbers of kit- of colony sizes from the early 1970s were made from aer- tiwakes attending colonies, and hence could not support the ial surveys (except for PLI), not with detailed counts as in hypothesis of Alliston et al. (1976). The exception was the 100 • M.L. MALLORY et al.

Baillie-Hamilton colony, the most remote from open water of all kittiwake colonies in Canada, where birds might have to cross 400 km of sea ice to reach open water in late ice years, especially if the polynya that forms in Queen’s Chan- nel beside the nesting island is small (Mallory and Fontaine, 2004). Colony counts were generally low in 2003 at all of the colonies, after two years of late, extensive sea ice and consequent low marine productivity. During those years, kit- tiwake breeding success was low at Prince Leopold Island, although colony attendance was average (Gaston et al., 2005b). Thus, extensive sea-ice cover may affect kittiwake breeding effort and success and consequent recruitment in later years, rather than immediate colony attendance. Such effects may be manifested at certain thresholds (i.e., non- linear relationship) or may occur across temporal scales that we could not address with these data. Black-legged kittiwake numbers are declining at many colonies around the North Atlantic Ocean (e.g., Freder- iksen et al., 2004), including West Greenland (Nyeland, 2004). However, our surveys suggest that this is not the case for colonies in eastern Nunavut, Canada, near the northern limit of the species’ range, and just west of declining Green- landic colonies. We expect that West Greenlandic and High Arctic Canadian kittiwakes probably mix during migration and possibly during the winter, which makes the contrasting trends surprising. Regional differences in population trends have also been reported recently for thick-billed murres across the North Atlantic (Irons et al., 2008), which may be linked to long-term patterns in oceanographic drivers of marine food webs. We currently lack sufficient data on the year-round ecology of High Arctic kittiwakes to specu- late reliably on why Canadian kittiwake numbers appear to have increased, while populations elsewhere have declined. Two information gaps must be filled before we can inter- pret trends in Arctic kittiwake populations. First, we need to determine the migratory pathways and wintering loca- tions of Canadian Arctic kittiwakes (e.g., by telemetry), to assess whether they are experiencing the same ecosystem constraints as declining populations elsewhere. Second, we need to conduct a current census at other colonies in Arctic Canada (Mallory and Fontaine, 2004) to determine whether the pattern we have observed in Barrow Strait can be FIG. 3. Relationships between distance to open water in the third week of June and site attendance, represented by (a) annual colony counts at smaller extrapolated to the majority of the Canadian Arctic breed- kittiwake colonies ( = Browne Island,  = Baillie-Hamilton Island, and  = ing population. Batty Bay) or (b) mean annual plot counts at Prince Leopold Island.

ACKNOWLEDGEMENTS REFERENCES We are grateful to numerous students and collaborators who worked at Prince Leopold Island over the years, to C. Baker for Alliston, W.G., Bradstreet, M.S.W., McLaren, M.A., Davis, R.A., assisting with one of the colony photo counts, and to A. Fontaine and Richardson, W.J. 1976. Numbers and distribution of birds for the count at Browne Island in 2003. Financial support was pro- in the central District of Franklin, NWT: June–August 1975. vided by Environment Canada (Canadian Wildlife Service), Indian 2 Vols. Unpubl. report by LGL Ltd., environmental research and Northern Affairs Canada (Northern Contaminants Program), associates for Polar Gas Project. Available from Canadian and Natural Resources Canada (Polar Continental Shelf Project). Wildlife Service, Environment Canada, 3rd Floor, Diamond John Chardine, Carsten Egevang, Aili Lage Labansen, and Greg Plaza, 5204–50th Avenue, Yellowknife, Northwest Territories Robertson provided insightful comments on the manuscript. X1A 1E2. HIGH ARCTIC KITTIWAKE COLONIES • 101

Baird, P.H. 1994. Black-legged kittiwake (Rissa tridactyla). In: Gaston, A.J., Gilchrist, H.G., and Mallory, M.L. 2005b. Variation in Poole, A., and Gill, F., eds. The birds of North America, No. ice conditions has strong effects on the breeding of marine birds 92. Philadelphia: The Birds of North America Inc. at Prince Leopold Island, Nunavut. Ecography 28:331–344. Braune, B.M. 2007. Temporal trends of organochlorines and Gaston, A.J., Mallory, M.L., Gilchrist, H.G., and O’Donovan, K. mercury in seabird from the Canadian Arctic, 1975–2003. 2006. Status, trends and attendance patterns of the northern Environmental Pollution 148:599–613. fulmar Fulmarus glacialis in Nunavut, Canada. Arctic Brown, R.G.B., Nettleship, D.N., Germain, P., Tull, C.E., and 59(2):165–178. Davis, T. 1975. Atlas of eastern Canadian seabirds. Ottawa: Irons, D.B., Anker-Nilssen, T., Gaston, A.J., Vernon Byrd, G., Canadian Wildlife Service. 220 p. Falk, K., Gilchrist, G., Hario, M., et al. 2008. Fluctuations in Cairns, D.K. 1987. Seabirds as indicators of marine food supplies. circumpolar seabird populations linked to climate oscillations. Biological Oceanography 5:261–271. Global Change Biology 14(7):1455–1463. Chapdelaine, G., and Brousseau, P. 1989. Size and trends of black- Mallory, M.L., and Fontaine, A.J. 2004. Key marine habitat sites legged kittiwake (Rissa tridactyla) populations in the Gulf of St. for migratory birds in Nunavut and the Northwest Territories. Lawrence (Québec) 1974–1985. American Birds 43:21–24. Occasional Paper Number 109. Ottawa: Canadian Wildlife Coulson, J.C. 1983. The changing status of the kittiwake Rissa Service. tridactyla in the British Isles, 1969–1979. Study Montevecchi, W.A. 1993. Birds as indicators of change in marine 30:9 –16. prey stocks. In: Furness, R.W., and Greenwood, J.J.D., eds. Birds Danchin, E., Boulinier, T., and Massot, M. 1998. Conspecific as monitors of environmental change. New York: Chapman and reproductive success and breeding habitat selection: Implications Hall. 217–266. for the study of coloniality. Ecology 79:2415–2428. Nettleship, D.N. 1974. Seabird colonies and distributions around Frederiksen, M., Wanless, S., Harris, M.P., Rothery, P., and Wilson, Devon Island and vicinity. Arctic 27(2):95–103. L.J. 2004. The role of industrial fisheries and oceanographic ———. 1977. Studies of seabirds at Prince Leopold Island and change in the decline of North Sea black-legged kittiwakes. vicinity, Northwest Territories: Preliminary report of biological Journal of Applied Ecology 41:1129–1139. investigations in 1975. Ottawa: Canadian Wildlife Service Gaston, A.J. 1988. Timing of breeding of kittiwakes Rissa Progress Notes 73. tridactyla and growth and diet of the chicks at Hantzsch Island, ———. 1980. A guide to the major seabird colonies of eastern NWT, Canada. Seabird 11:3–11. Canada: Identity, distribution, and abundance. Dartmouth, Gaston, A.J., and Hipfner, M. 1998. The effect of ice conditions in Nova Scotia: Canadian Wildlife Service, Atlantic Region. northern Hudson Bay on breeding by thick-billed murres (Uria 133 p. lomvia). Canadian Journal of Zoology 76:480–492. Nyeland, J. 2004. Apparent trends in the black-legged kittiwake in Gaston, A.J., Woo, K., and Hipfner, J.M. 2003. Trends in forage fish Greenland. Waterbirds 27:342–349. populations in northern Hudson Bay since 1981, as determined Robertson, G.R., Gilchrist, H.G., and Mallory, M.L. 2007. Colony from the diet of nestling thick-billed murres, Uria lomvia. dynamics and persistence of breeding in Canada. Arctic 56(3):227–233. Avian Conservation and Ecology 2:8. [online] URL: http:// Gaston, A.J., Gilchrist, H.G., and Hipfner, J.M. 2005a. Climate www.ace-eco.org/vol2/iss2/art8/. change, ice conditions and reproduction in an Arctic nesting Suryan, R.M., and Irons, D.B. 2001. Colony and population marine bird: Brünnich’s guillemot (Uria lomvia L.). Journal of dynamics of black-legged kittiwakes in a heterogeneous Applied Ecology 74:832–841. environment. Auk 118:636–649.